Normal and defective mariner-like elements in Rhynchosciara species (Sciaridae, Diptera)

Area of Science:

• Molecular Biology
• Genomics
• Evolutionary Biology

Background:

• Mariner-like elements are widespread mobile genetic elements found in eukaryotic genomes.
• These elements utilize a "cut-and-paste" transposition mechanism mediated by their encoded transposase.
• Understanding the diversity and evolution of these elements is crucial for genome dynamics.

Purpose of the Study:

• To investigate the presence and molecular characteristics of mariner-like elements in the genus Rhynchosciara.
• To compare these elements across different Rhynchosciara species.
• To elucidate the phylogenetic relationships of these elements to known mariner subfamilies.

Main Methods:

• Polymerase Chain Reaction (PCR) using primers from R. americana transposons (Ramar1, Ramar2).
• Amplification and sequencing of genomic DNA from four Rhynchosciara species.
• Molecular characterization of amplified sequences, including identification of terminal repeat sequences via inverse PCR.

Main Results:

• Identification of two distinct groups of mariner-like elements in Rhynchosciara: full-length and defective elements (Rmar1 and Rmar2).
• Defective elements contain deletions in the transposase open reading frame, leading to truncated proteins.
• Conserved amino acid blocks and a D,D(34)D motif were identified, though defective in some elements; phylogenetic analysis places them close to the mauritiana subfamily.

Conclusions:

• The genus Rhynchosciara harbors diverse mariner-like mobile elements, including both potentially active and defective forms.
• These elements share conserved features with other mariner elements, suggesting a common evolutionary origin.
• Inverted terminal repeats are critical for the mobility of these Rhynchosciara mariner-like elements.